Enhanced nitrification inhibitor composition

ABSTRACT

The present invention relates to an improved nitrification inhibitor composition and its use in agricultural applications.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation-in-part application of U.S. patentapplication Ser. No. 12/009,432, filed Jan. 18, 2008, which claims thebenefit of U.S. Provisional Application Ser. No. 60/881,680 filed onJan. 22, 2007, which is expressly incorporated by reference herein.

The present invention relates to an improved nitrification inhibitorcomposition and its use in agricultural applications.

BACKGROUND

(Trichloromethyl)pyridine compounds, such as nitrapyrin, have been usedas nitrification inhibitors in combination with fertilizers as describedin U.S. Pat. No. 3,135,594, which is herein incorporated by reference.These compounds maintain applied ammonium nitrogen in the ammonium form(stabilized nitrogen), which enhances crop performance. It would bedesirable to broadly apply these compounds with nitrogenous fertilizerat sowing time, but due to potential volatility losses, theseapplication methods are generally unsatisfactory. In addition nitrapyrinhas been added to anhydrous ammonia, which by default must be injectedinto the soil.

Other nitrapyrin formulations have been applied to the surface of thesoil, but must either be incorporated mechanically, or watered into thesoil within 8 hours after application to overcome volatility losses.Finally, rapid or dump release capsule formulations of nitrapyrinencapsulated with lignin sulfonates have also been disclosed in U.S.Pat. No. 4,746,513, which is incorporated herein by reference. However,although the release of nitrapyrin is delayed by the encapsulation, thecapsules release all of the nitrapyrin upon contact with moisture,exhibiting the same stability and volatility disadvantages of the priorapplication methods. Additionally, these formulations are difficult andcostly to produce and cannot be used with liquid urea ammonium nitrate(“UAN”) fertilizers.

Polycondensation encapsulation, as disclosed in U.S. Pat. No. 5,925,464,has been used to encapsulate agriculturally active ingredients,particularly to enhance handling safety and storage stability of theactive ingredient by using polyurethane rather than polyureaencapsulants.

However, there remains a need to deliver nitrification inhibitors suchas (trichloromethyl)pyridines, having greater long term stability in thefield environment, while maintaining the level of efficacy ofunencapsulated inhibitors.

SUMMARY

The present invention is a microcapsule suspension formulationcomprising:

(a) a suspended phase of a plurality of microcapsules having a volumemedian particle size of from about 1 to about 10 microns, wherein amicrocapsule comprises:

-   -   (1) a microcapsule wall produced by an interfacial        polycondensation reaction between a polymeric isocyanate and a        polyamine to form a polyurea shell having a weight percentage of        about 0.2 to about 15 percent of a total weight of the        microcapsule suspension formulation; and    -   (2) a (trichloromethyl)pyridine compound encapsulated within the        polyurea shell; and

(b) an aqueous phase including an ionic stabilizer.

The microcapsule suspension formulation of the present invention isstable and allows for delayed incorporation of nitrogen in crops, thusproviding agronomic and environmental benefits. Surprisingly it has beendiscovered that a composition of microcapsulated(trichloromethyl)pyridine compounds, such as nitrapyrin, has superiorperformance when compared to unencapsulated compositions of nitrapyrin,even when incorporated into the soil.

DETAILED DESCRIPTION

(Trichloromethyl)pyridine compounds useful in the composition of thepresent invention include compounds having a pyridine ring which issubstituted with at least one trichloromethyl group and mineral acidsalts thereof. Suitable compounds include those containing chlorine ormethyl substituents on the pyridine ring in addition to atrichloromethyl group, and are inclusive of chlorination products ofmethylpyridines such as lutidine, collidine and picoline. Suitable saltsinclude hydrochlorides, nitrates, sulfates and phosphates. The(trichloromethyl)pyridine compounds useful in the practice of thepresent invention are typically oily liquids or crystalline solidsdissolved in a solvent. Other suitable compounds are described in U.S.Pat. No. 3,135,594. A preferred (trichloromethyl)pyridine is2-chloro-6-(trichloromethyl)pyridine, also known as nitrapyrin, and theactive ingredient of the product N-SERVE™. (Trademark of DowAgroSciences LLC).

Examples of typical solvents which can be used to dissolve crystalline(trichloromethyl)pyridine compounds include aromatic solvents,particularly alkyl substituted benzenes such as xylene or propylbenzenefractions, and mixed naphthalene and alkyl naphthalene fractions;mineral oils; kerosene; dialkyl amides of fatty acids, particularly thedimethylamides of fatty acids such as the dimethyl amide of caprylicacid; chlorinated aliphatic and aromatic hydrocarbons such as1,1,1-trichloroethane and chlorobenzene; esters of glycol derivatives,such as the acetate of the n-butyl, ethyl, or methyl ether ofdiethyleneglycol and the acetate of the methyl ether of dipropyleneglycol; ketones such as isophorone and trimethylcyclohexanone(dihydroisophorone); and the acetate products such as hexyl or heptylacetate. The preferred organic liquids are xylene, alkyl substitutedbenzenes, such as propyl benzene fractions, and alkyl naphthalenefractions.

In general, the amount of solvent employed, if desired, is typicallyfrom about 40, preferably from about 50 to about 70, preferably to about60 weight percent, based on the total weight of a(trichloromethyl)pyridine/solvent solution. The amount of(trichloromethyl)pyridine within a (trichloromethyl)pyridine/solventsolution is typically from about 30, preferably from about 40 to about60, preferably to about 50 weight percent, based on the weight of a(trichloromethyl)pyridine/solvent solution.

The microcapsules useful in the present invention can be prepared by thepolycondensation reaction of a polymeric isocyanate and a polyamine toform a polyurea shell. Methods of microencapsulation are well known inthe art and any such method can be utilized in the present invention toprovide the capsule suspension formulation. In general, the capsulesuspension formulation can be prepared by first mixing a polymericisocyanate with a (trichloromethyl)pyridine/solvent solution. Thismixture is then combined with an aqueous phase which includes anemulsifier to form a two phase system. The organic phase is emulsifiedinto the aqueous phase by shearing until the desired particle size isachieved. An aqueous crosslinking polyamine solution is then addeddropwise while stirring to form the encapsulated particles of(trichloromethyl)pyridine in an aqueous suspension.

The desired particle size and cell wall thickness will depend upon theactual application. The microcapsules typically have a volume medianparticle size of from about 1 to about 10 microns and a capsule wallthickness of from about 10 to about 125 nanometers. In one embodiment,wherein the formulation of the present invention will be incorporatedimmediately into a growth medium, the desired particle size may be fromabout 2 to about 10 microns, with a cell wall of from about 10 to about25 nanometers. In another embodiment, requiring soil surface stability,the desired particle size may be from about 1-5 microns, with cell wallthicknesses of from about 75 to about 125 nanometers.

Other conventional additives may also be incorporated into theformulation such as emulsifiers, dispersants, thickeners, biocides,pesticides, salts and film-forming polymers.

Dispersing and emulsifying agents include condensation products ofalkylene oxides with phenols and organic acids, alkyl aryl sulfonates,polyoxyalkylene derivatives of sorbitan esters, complex ether alcohols,mahogany soaps, lignin sulfonates, polyvinyl alcohols, and the like. Thesurface-active agents are generally employed in the amount of from about1 to about 20 percent by weight of the microcapsule suspensionformulation.

The ratio of the suspended phase to the aqueous phase within themicrocapsule suspension formulation of the present invention isdependent upon the desired concentration of (trichloromethyl)pyridinecompound in the final formulation. Typically the ratio will be fromabout 1:0.75 to about 1:20. Generally the desired ratio is about 1:1 toabout 1:7, and is preferably from about 1:1 to about 1:4.

The presence of a (trichloromethyl)pyridine compound suppresses thenitrification of ammonium nitrogen in the soil or growth medium, therebypreventing the rapid loss of ammonium nitrogen originating from nitrogenfertilizers, organic nitrogen constituents, or organic fertilizers andthe like.

Generally, the microcapsule suspension formulation of the presentinvention is applied such that the (trichloromethyl)pyridine compound isapplied to the soil or a growth medium at a rate of from about 0.5 toabout 1.5 kg/hectare, preferably at a rate of from about 0.58 to about1.2 kg/hectare. The preferred amount can be easily ascertained by theapplication preference, considering factors such as soil pH,temperature, soil type and mode of application.

The microcapsule suspension formulation of the present invention can beapplied in any manner which will benefit the crop of interest. In oneembodiment the microcapsule suspension formulation is applied to growthmedium in a band or row application. In another embodiment, theformulation is applied to or throughout the growth medium prior toseeding or transplanting the desired crop plant. In yet anotherembodiment, the formulation can be applied to the root zone of growingplants.

Additionally, the microcapsule suspension formulation can be appliedwith the application of nitrogen fertilizers. The formulation can beapplied prior to, subsequent to, or simultaneously with the applicationof fertilizers.

The microcapsule suspension formulation of the present invention has theadded benefit that it can be applied to the soil surface, withoutadditional water or mechanical incorporation into the soil for days toweeks. Alternatively, if desired, the formulation of the presentinvention can be incorporated into the soil directly upon application.

The microcapsule suspension formulation of the present inventiontypically has a concentration of (trichloromethyl)pyridine compound inamounts of from about 5, preferably from about 10 and more preferablyfrom about 15 to about 40, typically to about 35, preferably to about 30and more preferably to about 25 percent by weight, based on the totalweight of the microcapsule suspension formulation. The microcapsulesuspension formulation is then mixed with a solvent or water to obtainthe desired rate for application.

Soil treatment compositions may be prepared by dispersing themicrocapsule suspension formulation in fertilizers such as ammonium ororganic nitrogen fertilizer. The resulting fertilizer composition may beemployed as such or may be modified, as by dilution with additionalnitrogen fertilizer or with inert solid carrier to obtain a compositioncontaining the desired amount of active agent for treatment of soil.

The soil may be prepared in any convenient fashion with the microcapsulesuspension formulation of the present invention, including mechanicallymixed with the soil; applied to the surface of the soil and thereafterdragged or diced into the soil to a desired depth; or transported intothe soil such as by injection, spraying, dusting or irrigation. Inirrigation applications, the formulation may be introduced to irrigationwater in an appropriate amount in order to obtain a distribution of the(trichloromethyl)pyridine compound to the desired depth of up to 6inches (15.24 cm.).

Surprisingly, once incorporated into the soil, the microcapsulesuspension formulation of the present invention outperforms othernitrapyrin formulations, especially unencapsulated versions. It wasthought that the encapsulated composition would not release nitrapyrinsufficiently to be as effective as the non-encapsulated versions,wherein the diffusion from the capsule would be too slow to provide abiological effect, but in fact the opposite effect is observed.

Due to the controlled release of nitrapyrin in the microcapsulesuspension formulation of the present invention, several advantages canbe attained. First, the amount of nitrapyrin can be reduced since it ismore efficiently released into the soil over an extended period of time.Additionally, the microcapsule suspension formulation of the presentinvention can be applied and left on the surface to be naturallyincorporated into the soil, without the need for mechanicalincorporation if desired.

Additionally, the microcapsule suspension formulation of the presentinvention can be combined or used in conjunction with pesticides,including arthropodicides, bactericides, fungicides, herbicides,insecticides, miticides, nematicides, nitrification inhibitors such asdicyandiamide, urease inhibitors such as N-(n-butyl) thiophosphorictriamide, and the like or pesticidal mixtures and synergistic mixturesthereof. In such applications, the microcapsule suspension formulationof the present invention can be tank mixed with the desired pesticide(s)or they can be applied sequentially.

Exemplary herbicides include, but are not limited to acetochlor,alachlor, aminopyralid, atrazine, benoxacor, bromoxynil, carfentrazone,chlorsulfuron, clodinafop, clopyralid, dicamba, diclofop-methyl,dimethenamid, fenoxaprop, flucarbazone, flufenacet, flumetsulam,flumiclorac, fluoroxypyr, glufosinate-ammonium, glyphosate,halosulfuron-methyl, imazamethabenz, imazamox, imazapyr, imazaquin,imazethapyr, isoxaflutole, quinclorac, MCPA, MCP amine, MCP ester,mefenoxam, mesotrione, metolachlor, s-metolachlor, metribuzin,metsulfuron methyl, nicosulfuron, paraquat, pendimethalin, picloram,primisulfuron, propoxycarbazone, prosulfuron, pyraflufen ethyl,rimsulfuron, simazine, sulfosulfuron, thifensulfuron, topramezone,tralkoxydim, triallate, triasulfuron, tribenuron, triclopyr,trifluralin, 2,4-D, 2,4-D amine, 2,4-D ester and the like

Exemplary insecticides include, but are not limited to

1,2 dichloropropane, 1,3 dichloropropene,

abamectin, acephate, acequinocyl, acetamiprid, acethion, acetoprole,acrinathrin, acrylonitrile, alanycarb, aldicarb, aldoxycarb, aldrin,allethrin, allosamidin, allyxycarb, alpha cypermethrin, alpha ecdysone,amidithion, amidoflumet, aminocarb, amiton, amitraz, anabasine, arsenousoxide, athidathion, azadirachtin, azamethiphos, azinphos ethyl, azinphosmethyl, azobenzene, azocyclotin, azothoate,

barium hexafluorosilicate, barthrin, benclothiaz, bendiocarb,benfuracarb, benoxafos, bensultap, benzoximate, benzyl benzoate, betacyfluthrin, beta cypermethrin, bifenazate, bifenthrin, binapacryl,bioallethrin, bioethanomethrin, biopermethrin, bistrifluoron, borax,boric acid, bromfenvinfos, bromo DDT, bromocyclen, bromophos, bromophosethyl, bromopropylate, bufencarb, buprofezin, butacarb, butathiofos,butocarboxim, butonate, butoxycarboxim,

cadusafos, calcium arsenate, calcium polysulfide, camphechlor,carbanolate, carbaryl, carbofuran, carbon disulfide, carbontetrachloride, carbophenothion, carbosulfan, cartap, chinomethionat,chlorantraniliprole, chlorbenside, chlorbicyclen, chlordane,chlordecone, chlordimeform, chlorethoxyfos, chlorfenapyr, chlorfenethol,chlorfenson, chlorfensulphide, chlorfenvinphos, chlorfluazuron,chlormephos, chlorobenzilate, chloroform, chloromebuform,chloromethiuron, chloropicrin, chloropropylate, chlorphoxim,chlorprazophos, chlorpyrifos, chlorpyrifos methyl, chlorthiophos,chromafenozide, cinerin I, cinerin II, cismethrin, cloethocarb,clofentezine, closantel, clothianidin, copper acetoarsenite, copperarsenate, copper naphthenate, copper oleate, coumaphos, coumithoate,crotamiton, crotoxyphos, cruentaren A &B, crufomate, cryolite,cyanofenphos, cyanophos, cyanthoate, cyclethrin, cycloprothrin,cyenopyrafen, cyflumetofen, cyfluthrin, cyhalothrin, cyhexatin,cypermethrin, cyphenothrin, cyromazine, cythioate,

d-limonene, dazomet, DBCP, DCIP, DDT, decarbofuran, deltamethrin,demephion, demephion O, demephion S, demeton, demeton methyl, demeton O,demeton O methyl, demeton S, demeton S methyl, demeton S methylsulphon,diafenthiuron, dialifos, diamidafos, diazinon, dicapthon,dichlofenthion, dichlofluanid, dichlorvos, dicofol, dicresyl,dicrotophos, dicyclanil, dieldrin, dienochlor, diflovidazin,diflubenzuron, dilor, dimefluthrin, dimefox, dimetan, dimethoate,dimethrin, dimethylvinphos, dimetilan, dinex, dinobuton, dinocap,dinocap 4, dinocap 6, dinocton, dinopenton, dinoprop, dinosam,dinosulfon, dinotefuran, dinoterbon, diofenolan, dioxabenzofos,dioxacarb, dioxathion, diphenyl sulfone, disulfuram, disulfoton,dithicrofos, DNOC, dofenapyn, doramectin,

ecdysterone, emamectin, EMPC, empenthrin, endosulfan, endothion, endrin,EPN, epofenonane, eprinomectin, esfenvalerate, etaphos, ethiofencarb,ethion, ethiprole, ethoate methyl, ethoprophos, ethyl DDD, ethylformate, ethylene dibromide, ethylene dichloride, ethylene oxide,etofenprox, etoxazole, etrimfos, EXD,

famphur, fenamiphos, fenazaflor, fenazaquin, fenbutatin oxide,fenchlorphos, fenethacarb, fenfluthrin, fenitrothion, fenobucarb,fenothiocarb, fenoxacrim, fenoxycarb, fenpirithrin, fenpropathrin,fenpyroximate, fenson, fensulfothion, fenthion, fenthion ethyl,fentrifanil, fenvalerate, fipronil, flonicamid, fluacrypyrim, fluazuron,flubendiamide, flubenzimine, flucofuron, flucycloxuron, flucythrinate,fluenetil, flufenerim, flufenoxuron, flufenprox, flumethrin,fluorbenside, fluvalinate, fonofos, formetanate, formothion,formparanate, fosmethilan, fospirate, fosthiazate, fosthietan,fosthietan, furathiocarb, furethrin, furfural,

gamma cyhalothrin, gamma HCH,

halfenprox, halofenozide, HCH, HEOD, heptachlor, heptenophos,heterophos, hexaflumuron, hexythiazox, HHDN, hydramethylnon, hydrogencyanide, hydroprene, hyquincarb,

imicyafos, imidacloprid, imiprothrin, indoxacarb, iodomethane, IPSP,isamidofos, isazofos, isobenzan, isocarbophos, isodrin, isofenphos,isoprocarb, isoprothiolane, isothioate, isoxathion, ivermectin jasmolinI, jasmolin II, jodfenphos, juvenile hormone I, juvenile hormone II,juvenile hormone III,

kelevan, kinoprene,

lambda cyhalothrin, lead arsenate, lepimectin, leptophos, lindane,lirimfos, lufenuron, lythidathion,

malathion, malonoben, mazidox, mecarbam, mecarphon, menazon,mephosfolan, mercurous chloride, mesulfen, mesulfenfos, metaflumizone,metam, methacrifos, methamidophos, methidathion, methiocarb,methocrotophos, methomyl, methoprene, methoxychlor, methoxyfenozide,methyl bromide, methyl isothiocyanate, methylchloroform, methylenechloride, metofluthrin, metolcarb, metoxadiazone, mevinphos,mexacarbate, milbemectin, milbemycin oxime, mipafox, mirex, MNAF,monocrotophos, morphothion, moxidectin,

naftalofos, naled, naphthalene, nicotine, nifluridide, nikkomycins,nitenpyram, nithiazine, nitrilacarb, novaluron, noviflumuron,

omethoate, oxamyl, oxydemeton methyl, oxydeprofos, oxydisulfoton,

paradichlorobenzene, parathion, parathion methyl, penfluoron,pentachlorophenol, permethrin, phenkapton, phenothrin, phenthoate,phorate, phosalone, phosfolan, phosmet, phosnichlor, phosphamidon,phosphine, phosphocarb, phoxim, phoxim methyl, pirimetaphos, pirimicarb,pirimiphos ethyl, pirimiphos methyl, potassium arsenite, potassiumthiocyanate, pp′ DDT, prallethrin, precocene I, precocene II, precoceneIII, primidophos, proclonol, profenofos, profluthrin, promacyl,promecarb, propaphos, propargite, propetamphos, propoxur, prothidathion,prothiofos, prothoate, protrifenbute, pyraclofos, pyrafluprole,pyrazophos, pyresmethrin, pyrethrin I, pyrethrin II, pyridaben,pyridalyl, pyridaphenthion, pyrifluquinazon, pyrimidifen, pyrimitate,pyriprole, pyriproxyfen,

quassia, quinalphos, quinalphos, quinalphos methyl, quinothion,quantifies,

rafoxanide, resmethrin, rotenone, ryania,

sabadilla, schradan, selamectin, silafluofen, sodium arsenite, sodiumfluoride, sodium hexafluorosilicate, sodium thiocyanate, sophamide,spinetoram, spinosad, spirodiclofen, spiromesifen, spirotetramat,sulcofuron, sulfuram, sulfluramid, sulfotep, sulfur, sulfuryl fluoride,sulprofos,

tau fluvalinate, tazimcarb, TDE, tebufenozide, tebufenpyrad,tebupirimfos, teflubenzuron, tefluthrin, temephos, TEPP, terallethrin,terbufos, tetrachloroethane, tetrachlorvinphos, tetradifon,tetramethrin, tetranactin, tetrasul, theta cypermethrin, thiacloprid,thiamethoxam, thicrofos, thiocarboxime, thiocyclam, thiodicarb,thiofanox, thiometon, thionazin, thioquinox, thiosultap, thuringiensin,tolfenpyrad, tralomethrin, transfluthrin, transpermethrin, triarathene,triazamate, triazophos, trichlorfon, trichlormetaphos 3, trichloronat,trifenofos, triflumuron, trimethacarb, triprene,

vamidothion, vamidothion, vaniliprole, vaniliprole,

XMC, xylylcarb,

zeta cypermethrin and zolaprofos.

Additionally, any combination of the above pesticides can be used.

Additionally, Rynaxypyr™, a new crop protection chemistry from DuPontwith efficacy in controlling target pests can be used.

The following examples are provided to illustrate the present invention.The examples are not intended to limit the scope of the presentinvention and they should not be so interpreted. Amounts are in weightparts or weight percentages unless otherwise indicated.

EXAMPLES Capsule Suspension Preparation

The weight percentages of the components for capsule suspensionpreparation are summarized in Table I. Total batch size is based on theweight of nitrapyrin used which is typically approximately 25 g. Theemulsifiers and crosslinking amines are added as aqueous solutions ofthe indicated concentrations. Microcapsule suspension formulationtechniques are known in the art. Additionally, it is also well know inthe art that the order of addition and corresponding procedures forproducing microcapsule suspension formulations may produce formulationshaving varying physical characteristics such as viscosity. The followingpreparation procedure is one illustrative embodiment of preparationprocedures, and should not be considered to limit the this application.

Oil soluble monomer PAPI 27 (polymethylene polyphenylisocyanate) (DowChemical), is added to a wide-mouthed jar. Nitrapyrin (Dow AgroSciences)and Aromatic 200 (Exxon) are then added in the form of a 50% nitrapyrinstock solution. The resulting organic phase is combined with an aqueoussolution of the emulsifier(s) as indicated in Table I. The resultingtwo-phase mixture is emulsified using a Silverson L4RT-A high-speedmixer fitted with the ¾ in. mixing tube and general purposeemulsification head. Emulsification is achieved by first mixing atrelatively low speed (˜1000 rpm) with the end of the mixing tube locatedin the aqueous phase to draw in the organic phase until well emulsified.The speed is then increased in discrete increments, measuring theparticle size after each increase. This process is continued until thedesired particle size is obtained. The water-solubleamine(diethylenetriamine (DETA, Aldrich) or ethylenediamine (EDA,Aldrich) solution (10 wt. % in water) is then added dropwise whilestirring at a reduced rate. Following the completion of the addition theresulting capsule suspension is stirred for an additional minute.Following capsule formation, Kelzan S (as 1.5% aqueous solution), Veegum(as 5% aqueous solution), Proxel GXL and the balance of the water wereadded as indicated in Table I and a final homogenization was performedwith the Silverson mixer.

TABLE I Example Compositions Weight Percent Material Ex. 1 Ex. 2 Ex. 3Ex. 4 Ex. 5 Ex. 6 Ex. 7 Nitrapyrin 9.46 9.47 9.45 9.47 9.45 9.35 12.76Aromatic 200 9.46 9.47 9.45 9.47 9.45 9.35 15.22 Dispersant/ 0.96¹ 0.48¹0.97¹ 0.48¹ 1.94¹ 2.43¹ 1.98⁴ Emulsifier (added as (added as (added(added as (added as (added (added 5% aq, 2.5% aq, as 5% 2.5% aq, 10% aq,as 10% as 5% sol'n) sol'n) aq, sol'n) sol'n) aq, aq, sol'n) sol'n)sol'n) Thickener² 0.15 0.15 0.15 0.15 0.15 0.15 0.02 Emulsifier 0.99⁵Suspending 0.2⁶ Aid PAPI-27 0.18 0.09 0.47 0.23 0.47 5.61 9.13 Amine0.04⁷ 0.02⁷ 0.11⁷ 0.06⁷ 0.13⁸ 1.35⁷ 2.19⁷ Biocide³ 0.1 0.1 0.1 0.1 0.10.1 0.1 Total Water 79.65 80.22 79.30 80.04 78.31 71.68 57.40 Calculated1.057 1.056 1.058 1.056 1.059 1.070 1.097 Density ¹Gohsenol GL-03(polyvinyl alcohol available from Nippon Gohsei) ²Kelzan S-Xanthan gum(available from CP Kelco) ³Proxel GXL (1,2-Benzisothiazol-3(2H)-oneavailable from Arch Chemicals, Inc.) ⁴Kraftsperse 25M (available fromMeadWestvaco) ⁵Tergitol 15-S-7 (available from The Dow Chemical Company)⁶Veegum (hectorite clay) (available from R.T. Vanderbilt Co., Inc.)⁷EDA-ethylenediamine (available from Aldrich) ⁸DETA-diethylenetriamine(available from Aldrich)

Particle Size Measurement of Capsules

Capsule suspension particle size distributions are determined using aMalvern Mastersizer 2000 light scattering particle sizer fitted with asmall volume sample unit. The volume median distribution (“VMD”) isreported for each formulation in Table II.

TABLE II Particle Size and Cell Wall Thickness Particle size ThicknessExample (μm) (nm) amine 1 5 10 EDA 2 10 10 EDA 3 5 25 EDA 4 10 25 EDA 52 10 DETA 6 2 100 EDA 7 2 100 EDA Concentration of nitrapyrin is 100 g/Lexcept for the formulation of Example 7 which is 140 g/l in theformulation based on the calculated density in Table I.EDA—ethylenediamine DETA—diethylenetriamine

Calculation of Wall Thickness

The calculation of the amounts of capsule wall components needed toachieve a target wall thickness is based on the geometric formularelating the volume of a sphere to its radius. If a core-shellmorphology is assumed, with the core comprised of the non wall-forming,water insoluble components (nitrapyrin, solvent) and the shell made upof the polymerizable materials (oil- and water-soluble monomers), thenequation (1) holds, relating the ratio of the volume of the core (V_(c))and the volume of the core plus the volume of the shell (V_(s)) to theirrespective radii, where r_(s) is radius of the capsule including theshell and 15 is thickness of the shell.

$\begin{matrix}{\frac{V_{c} + V_{c}}{V_{c}} = ( \frac{r_{s}}{r_{s} - l_{s}} )^{3}} & (1)\end{matrix}$

Solving equation (1) for the volume of the shell yields:

$\begin{matrix}{V_{s} = {V_{c}( {( \frac{r}{r_{s} - l_{s}} )^{3} - 1} )}} & (2)\end{matrix}$

Substituting masses (m_(i)) and densities (d_(i)) for their respectivevolumes (m_(s) ld_(s)=V_(s) and m_(c)ld_(c)=V_(c), where the subscript sor c refers to the shell or core, respectively) and solving for the massof the shell gives:

$\begin{matrix}{m_{s} = {m_{c}\frac{_{s}}{_{c}}( {( \frac{r_{s}}{r_{s} - l_{s}} )^{3} - 1} )}} & (3)\end{matrix}$

It can be seen by comparing equations (2) and (3) that the effect of thedensity ratio d_(s)/d_(c) is to apply a constant correction factor whenmasses are used to calculate the amounts of wall components needed toproduce a capsule of desired size and wall thickness. To be rigorous inthe calculation of m_(s), therefore, the densities of the core and shellmust be known or at least estimated from the weighted averages of thedensities of each of the components. However, the primary purpose ofthese calculations is to use capsule wall thickness as a convenientconceptual tool which would hopefully be helpful in understandingcapsule performance behavior and, therefore, in designing new capsuleformulations. Approximate values are felt to be sufficient for thispurpose. With this in mind the simplification is made of setting thevalue of d_(s)/d_(c) to 1, which yields equation (4).

$\begin{matrix}{m_{s} \approx {m_{c}( {( \frac{r_{s}}{r_{s} - l_{s}} )^{3} - 1} )}} & (4)\end{matrix}$

Making the substitutions m_(c)=m_(o)−m_(OSM),m_(s)=m_(o)+(f_(WSM/OSM)))m_(OSM)−m_(c), and f_(WSM/OSM)=m_(WSM)/m_(OSM)(the ratio of water soluble monomer to oil soluble monomer), where m_(o)is the total mass of the oil components (nitrapyrin, solvent,oil-soluble monomer), m_(OSM) is the mass of the oil-soluble monomer,and m_(WSM) is the mass of the water-soluble monomer, and solving form_(OSM) yields:

$\begin{matrix}{m_{OSM} = \frac{m_{O}( {( \frac{r_{s}}{r_{s} - l_{s}} )^{3} - 1} )}{f_{{WSM}/{OSM}} + ( \frac{r_{s}}{r_{s} - l_{s}} )^{3}}} & (5)\end{matrix}$

For the determination of mosM, the entire quantity of mwsM is used inthe calculation. In the present study the water-soluble monomer is usedat a 1:1 equivalent weight relative to the oil-soluble monomer for allof the capsule suspension preparations.

Conversely, the capsule wall thickness ls is calculated for each of thecapsule suspension preparations using the VMD particle size for thevalue of r_(s) and equation (6). These values are included in Table II.

$\begin{matrix}{l_{s} = \frac{r_{s}( {( \frac{m_{O} + {f_{{WSM}/{OSM}}m_{OSM}}}{m_{O} - m_{OSM}} )^{\frac{1}{3}} - 1} )}{( \frac{m_{O} + {f_{{WSM}/{OSM}}m_{OSM}}}{m_{O} - m_{OSM}} )^{\frac{1}{3}}}} & (6)\end{matrix}$

Examples 1-5

A bulk sample of Drummer silty clay loam (sic) soil is collected,air-dried and crushed to pass a 2-mm screen. Following the soilpreparation, approximately 25 grams of the processed soil is placed intobeakers and treated with 7.5 ml water containing 10 mg N (as (NH₄)₂SO₄)and 0.0, 0.25 or 0.50 ppm nitrapyrin (based on the weight of soilsample) using each of the Example formulations 1-5. The treated soil isthen evenly distributed over the soil surface and immediately coveredwith another 25 grams of soil. Three replications at each rate areprovided as well as three 50 gram soil samples without fertilizer orinhibitor addition and three replications of N-Serve 24 (DowAgroSciences) treated soil. Once liquid is absorbed into soil, thematerials are mixed to attain even distribution of thefertilizer/Example formulation. After mixing, water is added to bringsoil to field capacity. Beakers are unsealed, but covered to reduceevaporation and maintained at room temperature, approximately 25° C. Theamount of water lost from each beaker is measured at 5-day intervals andreplaced if the loss exceeds 2.5 ml.

On day 7, 14, 21, 28, 35, 42, 49, and 56 after initiation of theincubation, the soil contained in each individual beaker is dried,ground, and mixed. A subsample is analyzed for NH₄—N, as described byMulvaney, R. L. 1996; “Nitrogen-Inorganic Forms”, pg 1123-1184. In D. L.Sparks (ed.) Methods of soil analysis: Part 3/SSSA Book Ser.5.SSSA,Madison, Wis. If less than 30% of the N remains as ammonium in allreplications of any treatment, analysis of that treatment is ceased.Averages of the replications are provided in Table III and Table IV.

TABLE III 0.5 ppm Nitrapyrin PPM NH₄ Example Week 1 Week 2 Week 3 Week 4Week 5 No inhibitor 82.7 74.3 54.8 38.5 24.3 Control 1 82.3 84.2 67.759.6 48.9 2 82.5 79.5 71.3 63.1 49.8 3 81.8 78.8 67.6 64.3 46.7 4 88.581.8 77.5 55.6 46.1 5 82.9 78.0 70.8 57.0 51.7 N-Serve 24 87.1 75.5 64.955.6 37.4

TABLE IV 0.25 ppm Nitrapyrin PPM NH₄ Example Week 1 Week 2 Week 3 Week 4Week 5 No inhibitor 82.7 74.3 54.8 38.5 24.3 Control 1 83.2 79.6 68.057.3 43.9 2 82.6 78.4 64.7 53.6 42.4 3 81.4 73.8 61.1 50.7 37.9 4 78.572.6 60.3 48.5 37.3 5 83.5 78.1 61.0 48.0 35.1 0.5 N-Serve 24 87.1 75.564.9 55.6 37.4

The microencapsulated formulations are compared to the nitrapyrinN-Serve 24 (available from Dow AgroSciences) formulation at the samerate. At Week 5 all five encapsulated formulations are outperformingN-Serve 24, demonstrating that at the same rate they provide superiorresidual nitrogen-stabilizing performance.

Examples 6 and 7

All of the following examples further include an ionic stabilizerincluded in the aqueous phase. In the illustrative example, sodiumdioctylsulphosuccinate (Geropon SDS, available from Rhodia) was used.Any other suitable ionic stabilizer may be used.

Four replications each of Example 6 and 7 formulations, and N-Serve 24(0.5 lb a.i./acre; 0.58 kg/hectare) in combination with urea ammoniumnitrate (160 lb/acre; 181.5 kg/hectare), as well as four replications ofurea ammonium nitrate (160 lb N/acre; 181.5 kg/hectare) with 0nitrification inhibitor treatment are applied to Drummer sicl samplesclear of vegetation.

Following application of the example formulations, the formulations areincorporated immediately with moisture. Once incorporation occurs,treatments are open to native rainfall and environmental effects.

Soil samples are collected from each treatment and analyzed for NH₄—N asdescribed by Mulvaney, as referenced previously, at 21, 28, 35, 42, 49and 56 days after incorporation. Samples are collected from 0-3 inch(0-7.6 cm), depths for 8 weeks with additional samples collected from a3-6 inch (7.6 cm-15.2 cm) depth in weeks 7 and 8 after the firsttreatment is incorporated. On the day of application, samples arecollected from the 0-3 inch (0-7.6 cm) depth for NH₄—N analysis.

The effectiveness of a nitrification inhibitor to keep nitrogen in theammonia form is measured by analyzing soil samples for the presence ofthe ammonium molecule (NH₄). Averages of the replications are reportedin Table V.

TABLE V Immediate incorporation of Controls and Examples 6 and 7 PPM NH₄Week Week Week Example 3 4 5 Week 6 Week 7 Week 8 Week 9 N-Serve-24 27.415.6 10.2 12.6 8.3 4.2 7.0 Comparison UAN 16.7 13.3 5.3 7.0 7.2 4.0 5.0Control Example 6 24.9 19.2 8.5 10.2 6.6 3.6 5.5 Example 7 26.4 22.016.3 12.4 9.1 5.8 6.0 UAN—Urea ammonium nitrate

In a further analysis, the nitrification inhibition of Examples 6 and 7are coupled with the surface stability of those formulations. The UANalone and the UAN+N-Serve treatments are moisture incorporated on theday of application to the soil while the two example formulations lay onthe soil surface for a week prior to incorporation. Plots awaitingmoisture incorporation are protected from moisture when rain events arethreatening. Results are listed in TABLE VI.

TABLE VI Delayed incorporation for Examples 6 and 7 PPM NH₄ Examplesweek 2 week 3 week 4 week 5 week 6 week 7 week 8 week 9 N-Serve-24 42.335.1 24.6 18.8 30.0 17.2 19.4 24.4 Comparison UAN Control 48.4 34.9 22.816.2 26.7 15.4 21.5 19.0 Example 6 50.6 41.6 30.2 22.4 34.0 18.6 27.028.5 Example 7 54.0 55.6 39.1 40.9 40.0 25.6 31.4 34.4

Both Examples 6 and 7 are more effective at nitrification inhibitionthan N-Serve 24.

Examples 8 and 9

The weight percentages of the components for capsule suspensionpreparation are listed in Table VII. Total batch size is 2.1 kg (Example8) or 185 g (Example 9). Oil soluble monomer PAPI 27 (polymethylenepolyphenylisocyanate, Dow Chemical), is added to a wide-mouthed jar.N-Serve TG (Dow AgroSciences; 90 wt % nitrapyrin) and Aromatic 200(Exxon) are then added in the form of a nitrapyrin technicalconcentrated stock solution. The resulting homogeneous organic phase iscombined with an aqueous solution composed of Kraftsperse 25M, Tergitol15-S-7, Geropon SDS, and Proxcel GXL.

The resulting two-phase mixture is emulsified using a Silverson L4RT-Ahigh-speed mixer fitted with the ¾ in. mixing tube and general purposeemulsification head. Emulsification is achieved by first mixing atrelatively low speed (˜1000 rpm) with the end of the mixing tube locatedin the aqueous phase to draw in the organic phase until well emulsified.The speed is then increased in discrete increments, measuring theparticle size after each increase. This process is continued until thedesired particle size (2.5 micron) is obtained.

The water-soluble amine ethylenediamine aqueous solution (20 wt % inexample 8; wt % in example 9, example 10, and example 11) is then addeddropwise while stirring at a reduced rate. Following the completion ofthe addition the resulting capsule suspension is stirred for anadditional time to have the polyurea shell forming reaction to be fullycompleted. Following capsule formation, finishing phase including Avicel(as 5 wt % aqueous solution, Kelzan (as 1.5 wt % aqueous solution),Proxel GXL and the balance of the water were added as indicated in TableVII and a final homogenization was performed with the Silverson mixer.The dispersed phase, including nitrapyrin, aromatic 200, PAPI 27, andethylene diamine, is 49.55 wt % (example 8) or 55.94 wt % (example 9).

Example 10

The weight percentages of the components for capsule suspensionpreparation are listed in Table VII. Total batch size is 100 kilograms.The processing is demonstrated in Scheme 1 (A). A homogenous solution ofN-Serve TG (Dow AgroSciences, 90 wt % nitrapyrin) and Aromatic 200(Exxon) is prepared by melting N-Serve TG and adding it to the solvent.To this, the oil soluble monomer PAPI 27 is added and mixed together tocreate the Oil Phase. The Aqueous Phase is prepared by mixingKraftsperse 25M, Tergitol 15-S-7, Geropon SDS, Proxel GXL, Antifoam 100IND and water into a homogeneous solution.

The Oil Phase and Aqueous Phase are metered together in a 1.25:1.0 ratiothrough a rotor/stator homogenizer cell to create an emulsion of thedesired particle size (2.5 micron). This process continues until the oilphase is depleted. The batch is cooled down to below 15° C. before theamine is added. The 30 weight % amine is added into the batch underagitation. The reaction vessel is stirred for a minimum of 2 hoursbefore the viscosity components are added. The viscosity phase consistsof 5 w/w % Avicel, 1.5 w/w % Kelzan S, 1% Proxel GXL and water.Additional water is added if necessary to achieve the target assay, thenthe batch is packaged for final use.

Example 11

The weight percentages of the components for capsule suspensionpreparation are listed in Table VII. Total batch size is 400 kilograms.The processing is demonstrated in Scheme 1 (B). A homogenous solution ofN-Serve TG (Dow AgroSciences, 90 wt % nitrapyrin) and Aromatic 200(Exxon) is prepared by melting N-Serve TG and adding it to the solvent.To this, the oil soluble monomer PAPI 27 is added and mixed together tocreate the Oil Phase. The Aqueous Phase is prepared by mixingKraftsperse 25M, Tergitol 15-S-7, Geropon SDS, Proxel GXL, Antifoam 100IND and water into a homogeneous solution.

The Oil Phase and Aqueous Phase are metered together in a 1.25:1.0 ratiothrough a rotor/stator homogenizer cell to create an emulsion of thedesired particle size (2.5 micron). This process continues until the oilphase is depleted. The batch is cooled down to below 15° C. before theamine is added. The 30 weight % amine is added into the batch by using aside stream circulation stream pumping the emulsion at a rate of 100liters per minute. The amine is added in less than 10 minutes,preferably less than 5 minutes, to set the capsules walls. The reactionvessel is stirred for a minimum of 2 hours before the viscositycomponents are added. The viscosity phase consists of 5 w/w % Avicel,1.5 w/w % Kelzan S, 1% Proxel GXL and water. Additional water is addedif necessary to achieve the target assay, then the batch is packaged forfinal use.

TABLE VII Example Compositions Weight Percent (wt %) Material Example 8Example 9 Example 10 Example 11 N-Serve TG 19.78 23.68 19.63 19.63Aromatic 200 18.91 22.65 18.78 18.78 PAPI-27 8.87 7.72 8.80 8.80Dispersant¹ 1.19 1.18 1.18 1.18 Emulsifier² 1.19 1.18 1.18 1.18 IonicStabilizer³ 0.24 0.24 0.24 0.24 Antiformer⁴ 0.09 0.09 0.09 Biocide⁵ 0.120.12 0.12 0.12 Amine⁶ 1.99^(a) 1.90^(b) 1.97^(c) 2.17^(c) SuspendingAid⁷ 0.19 0.22 0.19 0.19 Thickener⁸ 0.03 0.03 Total Water 47.52 41.0247.79 47.59 ¹Kraftsperse 25M (available from MeadWestvaco) ²Tergitol15-S-7 (available from The Dow Chemical Company) ³Geropon SDS (sodiumdioctylsulphosuccinate available from Rhodia) ⁴Antiform 100 IND(available from Harcros Chemicals Inc.) ⁵Proxel GXL(1,2-Benzisothiazol-3(2H)-one available from Arch Chemicals, Inc.)⁶EDA-ethylenediamine (available from Aldrich) in ^(a)20 wt %; ^(b)50 wt%; and ^(c)30 wt % aqueous solution ⁷Avecel (available from FMCBiopolymer) ⁸Kelzan S-Xanthan gum (available from CP Kelco)

1. A microcapsule suspension formulation comprising: (a) a suspendedphase of a plurality of microcapsules having a volume median particlesize of from about 1 to about 10 microns, wherein a microcapsulecomprises: (1) a microcapsule wall produced by an interfacialpolycondensation reaction between a polymeric isocyanate and a polyamineto form a polyurea shell having a weight percentage of about 0.2 toabout 15 percent of a total weight of the microcapsule suspensionformulation; and (2) a (trichloromethyl)pyridine compound encapsulatedwithin the polyurea shell; and (b) an aqueous phase including an ionicstabilizer.
 2. The microcapsule suspension formulation of claim 1wherein the tri(chloromethyl)pyridine compound is2-chloro-6-(trichloromethyl)pyridine.
 3. The microcapsule suspensionformulation of claim 1 wherein the microcapsules have a volume medianparticle size of from about 1 to about 5 microns.
 4. The microcapsulesuspension formulation of claim 1 wherein the ratio of the suspendedphase a) to the aqueous phase b) is from about 1:0.75 to about 1:20. 5.The microcapsule suspension formulation of claim 1 wherein the ratio ofthe suspended phase a) to the aqueous phase b) is from about 1:1 toabout 1:7.
 6. The microcapsule suspension formulation of claim 1 whereinthe ratio of the suspended phase a) to the aqueous phase b) is fromabout 1:1 to about 1:4.
 7. The microcapsule suspension formulation ofclaim 1 wherein the polymeric isocyanate is polymethylenepolyphenylisocyanate.
 8. The microcapsule suspension formulation ofclaim 1 wherein the polyamine is selected from ethylenediamine anddiethylenetriamine.
 9. A fertilizer composition comprising: a nitrogenfertilizer and the microcapsule suspension formulation of claim
 1. 10.The fertilizer composition of claim 9 wherein the nitrogen fertilizer isurea ammonium nitrate.
 11. A method of suppressing the nitrification ofammonium nitrogen in growth medium comprising applying the microcapsulesuspension formulation of claim 1 to said growth medium.
 12. The methodof claim 11 wherein the formulation is incorporated into the growthmedium.
 13. The method of claim 11 wherein the formulation is applied toa growth medium surface.
 14. The method of claim 11 wherein theformulation is applied in combination with a pesticide or sequentiallywith a pesticide.
 15. The method of claim 11 wherein the formulation isapplied with a nitrogen fertilizer.
 16. The method of claim 15 whereinthe nitrogen fertilizer is urea ammonium nitrate.
 17. The method ofclaim 1, wherein the ionic stabilizer is sodium dioctylsulphosuccinate.18. The method of claim 1, wherein the ionic stabilizer is from about0.01 to about 0.5 weight of the microcapsule suspension formulation.